feat: remove dev_session, add Drizzle schema + RLS + real auth

BREAKING: dev_session cookie bypass removed. Admin access now requires
a real Auth.js v5 session (Google OAuth in production). Provision users
by inserting into users + tenant_users tables.

New in this commit:
- db/migrations/0001_init.sql: 18-table SaaS schema with RLS (tenants,
  users, tenant_users, plans, add_ons, subscriptions, tenant_add_ons,
  products, product_images, stops, customers, orders, order_items,
  brand_settings, email_templates, campaigns, files, audit_log)
- db/schema/: Drizzle TypeScript mirror of every table
- db/client.ts: withTenant() / withPlatformAdmin() query wrappers that
  set Postgres GUCs (app.current_tenant_id, app.platform_admin) for
  RLS enforcement. Never query a tenant-scoped table without one.
- db/seed.ts: seeds 3 plans, 6 add-ons, 2 tenants (Tuxedo, Indian River
  Direct), brand_settings, sample products/stops/customers
- scripts/migrate.js: applies migrations in lexical order with tracking
- scripts/db-reset.js: drops + recreates DB, runs migrate + seed
- DATABASE_URL now uses rc_app (non-superuser, NOBYPASSRLS). RLS is
  enforced even for the app user. DATABASE_ADMIN_URL for migrations.
- src/lib/admin-permissions.ts: getAdminUser() reads Auth.js session,
  looks up user + tenant in Postgres. brand_id kept as alias for
  backward compat.
- src/middleware.ts: Auth.js-only route protection, dev_session gone
- src/app/login/LoginClient.tsx: Google OAuth only, no demo mode
- src/components/admin/AdminSidebar.tsx + AdminHeader.tsx: signOutAction
  replaces supabase signout
- @/db/* path aliases in tsconfig.json + vitest.config.ts
- drizzle.config.ts added
- db/auth_schema.sql removed (was a stub; replaced by real schema)
- src/app/api/dev-login/route.ts deleted
- tests: updated to remove dev_session coverage

vitest.config.ts

@@ -5,10 +5,12 @@ import path from "node:path";
 export default defineConfig({
   plugins: [react()],
   resolve: {
-    alias: {
-      // Mirrors `tsconfig.json` paths: { "@/*": ["./src/*"] }
-      "@": path.resolve(__dirname, "src"),
-    },
+    alias: [
+      { find: /^@\/(?!db)/, replacement: path.resolve(__dirname, "src") + "/" },
+      { find: "@/db/client", replacement: path.resolve(__dirname, "db/client.ts") },
+      { find: "@/db/schema", replacement: path.resolve(__dirname, "db/schema/index.ts") },
+      { find: "@/db", replacement: path.resolve(__dirname, "db") },
+    ],
   },
   test: {
     environment: "node",